js实现水波纹背景
Posted 亦心晗
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<!DOCTYPE html> <html> <head> <title>水波背景</title> <meta charset="utf-8" /> <style> html, body {width:100%; height:100%; padding:0; margin:0;} </style> </head> <body> <canvas id="canvas" style="position:absolute;top:0px;left:0px;z-index:1;"></canvas> <script type="text/javascript"> //获得canvas容器 var canvas = document.getElementById(‘canvas‘); //获得画笔 var ctx = canvas.getContext(‘2d‘); //canvas设置宽度 canvas.width = canvas.parentNode.offsetWidth; //canvas设置高度 canvas.height = canvas.parentNode.offsetHeight; //如果浏览器支持requestAnimFrame则使用requestAnimFrame否则使用setTimeout window.requestAnimFrame = (function(){ return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function( callback ){ window.setTimeout(callback, 1000 / 60); }; })(); // 波浪大小 var boHeight = canvas.height / 10; var posHeight = canvas.height / 1.2; //初始角度为0 var step = 0; //定义三条不同波浪的颜色 var lines = ["rgba(0,222,255, 0.2)", "rgba(157,192,249, 0.2)", "rgba(0,168,255, 0.2)"]; function loop(){ //清除canvas内容 ctx.clearRect(0,0,canvas.width,canvas.height); step++; //画3个不同颜色的矩形 for(var j = lines.length - 1; j >= 0; j--) { ctx.fillStyle = lines[j]; //每个矩形的角度都不同，每个之间相差45度 var angle = (step+j*50)*Math.PI/180; var deltaHeight = Math.sin(angle) * boHeight; var deltaHeightRight = Math.cos(angle) * boHeight; ctx.beginPath(); ctx.moveTo(0, posHeight+deltaHeight); ctx.bezierCurveTo(canvas.width/2, posHeight+deltaHeight-boHeight, canvas.width / 2, posHeight+deltaHeightRight-boHeight, canvas.width, posHeight+deltaHeightRight); ctx.lineTo(canvas.width, canvas.height); ctx.lineTo(0, canvas.height); ctx.lineTo(0, posHeight+deltaHeight); ctx.closePath(); ctx.fill(); } requestAnimFrame(loop); } loop(); </script> </body> </html>
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